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Abstract
Spectrin is a major protein of the red cell membrane, and is composed of alpha- and beta-subunits. While spectrin was initially thought to be specific for erythrocytes, similar, but nonidentical peptides have recently been identified in other tissues, including lens, suggesting the existence of a spectrin gene family. To study the nature of spectrin-like peptides in the lens, we examined the transcription of erythroid and nonerythroid spectrin in human lens and cerebellum by direct hybridization with known human alpha- and beta-spectrin cDNA (erythroid probes), as well as with a human alpha-fodrin cDNA (nonerythroid probe). Northern blots of poly(A)+ RNA from erythroid, as well as several nonerythroid cells, and the total RNA from lens, showed that the beta-spectrin cDNA probe hybridized to two distinct bands of 8.6 and 7.4 kb mRNA in human lens, and was present in abundance. The erythroid beta-spectrin 11 kb mRNA transcript was also found in the human cerebellum. The beta-spectrin transcripts from these nonerythroid tissues were found to have different sizes compared to the major erythroid 7.8 kb beta-spectrin mRNA. Human lens contained a 7.5 kb transcript of the erythroid alpha-spectrin subunit. In addition, the human lens was found to have a 7.2 kb alpha-fodrin transcript; while the cerebellum had an 8.5 kb alpha-fodrin mRNA, the same size as that found in other nonerythroid tissues. The abundance of erythroid and nonerythroid spectrin transcripts in lens was significantly greater than in any other tissues examined. These data show that the human lens has abundant erythroid alpha- and beta-spectrin transcripts, as well as a unique alpha-fodrin transcript.(ABSTRACT TRUNCATED AT 250 WORDS)